The Claim: Timing and Sexual Position Can Influence a Baby’s Sex

For couples who know they want a girl or a boy, there is always the fertility clinic. But is there a lower-tech method?

A technique called the Shettles method, popularized in the 1960s, holds that couples can increase their odds of having a boy by, among other things, having intercourse as close to ovulation as possible. Intercourse two to three days before ovulation, preferably in the missionary position, supposedly heightens the odds of having a girl.

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Credit...Leif Parsons

The premise is that sperm carrying the X and Y chromosomes have different characteristics, and that each is more likely to fertilize the egg — which is always X — in different circumstances.

But don’t count on it. Several studies have tried to confirm the claim but found no effect. In 1991, researchers at Johns Hopkins analyzed the findings of six previous studies on the subject. They found that relying on timing and position for “natural family planning” did not work.

A later study, in The New England Journal of Medicine, followed 221 healthy women who were planning a pregnancy. Of those, 192 became pregnant during the study period. Again, the researchers found no timing effect.

THE BOTTOM LINE

According to studies, timing and sexual position do not influence the sex of the baby.